Supply of electric discharge tubes excited inductively



Dec. 3, 1940. J. BETHENOD 2,223,399

SUPPLY OF ELECTRIC DISCHARGE TUBES EXCITED INDUCTIVELY Original Filed Oct. 14, 1935 JOSEPH BETHENOD all"): up.

Patented Dec. 3, 1940- UNITED STATES SUPPLY OF ELECTRIC DISCHARGE TUBES EXCITED INDUCTIVELY Joseph Bethenod, Paris, France, assignor to:

Socit Anonyme pour les Applications de lElectricite et des Gaz Bares, Etablissements Claude-Paz & Silva, Paris. France Original application October 14, 1935, Serial No. 44,983. Divided and this application August 25, 1938, Serial No. 226,826. In France October 1 Claim. (01. ire-124) This application is a division of .my earlier application Serial No. 44,983 filed October 14, 1935. a The present invention relates to a method of supply of electric gas discharge devices by means of a source of periodic current of high frequency brought into communication with the ends of an inductance coil inductively coupled with the gas-, eous medium of the device, for the purpose of producing and maintaining in this gaseous medium a discharge with spark spectrum.

The present invention refers to the case in which in such an arrangement the passage through the coil of a current corresponding to the starting current for this discharge would produce excessive heating of the coil. This occurs especially when the frequency of the supply current does not exceed that which can be produced industrially by a high frequency alternator, say about 30,000 cycles per second. In order to attain the considerable electric field to be induced in the gaseous medium for the obtaining of the said discharge, it would then be necessary to bring the current through the coil to such an extremely high value that if. continued after the starting of the device, it would give rise to excessive heating of the coil.

' The present invention has for its object means permitting the field in question to be easily ob- ;tained while avoiding the above mentioned drawback.

According to the invention, the inductance coil being supplied with alternating current of 'an intensity below that necessary to start a discharge in the gaseous medium yielding a spark spectrum 5 and below that producing an excessive heating of the coil but above that necessary to maintain in initiated discharge in that gaseous medium yielding a. spark spectrum, there is employed an electrode positioned externally and in the vicinity of the discharge device, and connected to a source of suitable potential and frequency to electrostatically induce in the gaseous medium a current supplementing the current induced by the coil,

the resultant of said currents being of suflicient intensity to start in the gaseous medium the discharge with spark spectrum. The supply of current to said electrode may be cut off after starting of said discharge.

- In the accompanying drawing is shown. by way of example only, a diagram in accordanace with a by the coil I.

the present invention; The inductance coil I is lodged in a close-fitting cylindrical cavity formed in the envelope of the tube 2 and extends into the interior of this tube. The winding is fed by the source 3 of periodic current at high fre- 5 'quency and constant amplitude which can be regarded as a high frequency alternator. 1 is a source of current feeding the auxiliary electrode 9 which is placed outside and near the tube and forms a condenser withthe winding I in 10 such a manner as to give rise in the tube to an electric field additional to that directly formed The voltage and the frequencyrof the source I are suitably selected to permit starting in the tube of a spark spectrum,- the strength 15 of the current in the coil, moreover, being determined in such a manner as to permit maintenance of the-feed spectrum without giving rise to excessive heating of this winding. The switch 8 serves to close the supply circuit of the induc- 2o tance winding, and the switch 8 that of the auxiliary electrodes.

What I claim is:

In combination, a gaseous discharge device 25 having a gaseous medium therein, a coil so inductively coupled to the gaseous medium in said discharge device that a spark spectrum may be produced in said medium by energizing said coil, said coil being mounted within a reentrant por- 30 tion of the enclosing vessel, means for supplying alternating current having a frequency of the order of- 30,000 cycles to said coil of an intensity below that necessary to start a discharge in said gaseous medium yielding a spark spectrum and below that producing an excessive heating of the coil but above that necessary to maintain an initiated discharge in said gaseous medium yielding a spark spectrum, an electrode positioned externally of said device at a point opposite said energizing coil, means for supplying a high frequency alternating potential between said external electrode and said coil to electrostatically induce in said, gaseous medium a current supplementing the current induced by said coil, the resultant of 5 said currents being of sufiicient intensity to start 4 a discharge in the gaseous medium yielding a spark spectrum, and means for cutting'oif the supply of current to said electrode after starting of said discharge. m

JOSEPH BETHENOD. 

